Keeping Derrelle Revis would make coach Rex Ryan happy and give him a chance to field a top-five defense, but only delirious diehards would try to make a case that this has a chance to be a playoff team in 2013, writes The Post’s Steve Serby. (
)

David Garrard was on a Jets conference call yesterday talking about how excited he is that he has been promised an opportunity to unseat Mark Sanchez as the starting quarterback.

Watch your back, Sanchise, this guy is a threat.

This isn’t Tim Tebow. This isn’t a Wildcat. It is a wild card.

But it is this simple: Until the Jets find themselves a franchise quarterback who can make Tom Brady and Bill Belichick sweat, they will remain irrelevant Buttfumblers playing in a deserted stadium with a new head coach and fourth offensive coordinator in four years.

It is a big reason why they should trade Darrelle Revis, so they can add resources to find that franchise quarterback in a quarterback-driven league, so they have the kind of salary-cap flexibility they will need for the most important position in the field.

Keeping Revis would make coach Rex Ryan happy and give him a chance to field a top-five defense, but after what we have seen from Sanchez these past two seasons, and what we haven’t seen from the injury-plagued Garrard these last two seasons, only delirious diehards who bleed Jets green would try to make a case that this has a chance to be playoff team in 2013.

Forget Brady for a moment. Look around the AFC. The Dolphins secured their franchise quarterback last year, and now Ryan Tannehill gets to throw deep to Mike Wallace. The Bills, after cutting Ryan Fitzpatrick, will now draft their franchise quarterback (Geno Smith? Matt Barkley?) probably with the eighth pick, one slot in front of the Jets.

The Colts sucked for Andrew Luck, and suck no more. Andy Reid and the Chiefs filled their quarterback black hole with the competent Alex Smith. The Ravens locked up Joe Flacco. The Bengals have been to back-to-back playoffs with Andy Dalton, although the Jets were blaring that trumpet about the Sanchise two years ago.

The Titans don’t know yet whether they were right on Jake Locker, same with the Jaguars on Blaine Gabbert. Same with the Browns on Brandon Weeden.

The 49ers (Colin Kaepernick, second round) and Seahawks (Russell Wilson, third round) have reminded us that you can find your franchise quarterback after the first round. In which case someone such as Ryan Nassib of Syracuse, or perhaps E.J. Manuel of Florida State would make sense for the Jets in the second round.

What started the Jets down this road to ruin was missing on Kellen Clemens. Mike Tannenbaum and Eric Mangini smartly drafted D’Brickashaw Ferguson and Nick Mangold in the first round in 2006 and passed on Vince Young, Matt Leinart and Jay Cutler — in part because they saw Clemens as their quarterback of the future. Ouch.

And so Chad Pennington begat Brett Favre who begat Sanchez who begets Garrard.

A healthy Garrard, with his professionalism and leadership and mobility and familiarity with the West Coast system and penchant for avoiding grievous interceptions and Buttfumbles, is no long shot to beat out Sanchez.

“My knee is great right now,” Garrard said.

This will mark the first time in his five years that Sanchez had a legitimate contender for his job.

The good news, for those of you who have not taken a Lambeau Leap off the Sanchez bandwagon, is that there is nowhere to go but up, that if Sanchez can survive the Tim Tebow circus, he can survive anything, that Marty Mornhinweg will be an upgrade over Tony Sparano.

Then again, Sanchez — or Garrard — isn’t any less set up to fail given his supporting cast. Will tight end Dustin Keller leave? Will Brandon Moore leave? Will Santonio Holmes act up and out? Will Stephen Hill drop the dropsies once and for all? Who’s the running back?